Many types of input devices may be used to provide input to computing devices, such as buttons or keys, mice, trackballs, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation. Typically touch screens can include a touch sensor panel, which may be optically clear or near-clear, and a display device that can be positioned behind, in front of or in plane with the panel so that the touch-sensitive surface substantially covers the viewable area of the display device. Touch screens allow a user to provide various types of input to the computing device by touching the touch sensor panel using a finger, stylus, or other object at a location dictated by a user interface being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
Touch sensor panels can be formed from a matrix of row and column traces, with sensors or touch regions present where the rows and columns cross over each other while being separated by a dielectric material. Each row can be driven by a stimulation signal, and touch locations can be identified through changes in the stimulation signal. Typically, a touch location is sensed based on an interference of the stimulation signal, such that a touch location may correspond to a location where the stimulation signal is the weakest. In some instances it may be desirable for a user to provide input to the touch screen with an input device other than the user's finger or fingers. Some input devices, such as a stylus, allow a user to use the input device as a pen or pencil and “write” on the touch screen. However, many times, a tip or point of these input devices may be a relatively hard element that may feel unnatural to users, as well as may generally produce the same output on the touch screen regardless of the user's input variation (such as, pressing harder, angling the tip, and so on). Accordingly, many of the “writing” input devices may lack features that may be present in pens, pencils, or other non-electronic writing tools.